Method and apparatus for teaching a plurality of keys to an authorization device in a vehicle, wherein the keys that are in a reception range of a transmission unit of the authorization device receive a test signal from said authorization device and transmit a response signal to the authorization device in response to said test signal.
Such methods and apparatuses are used in vehicle construction to teach the keys associated with a vehicle to an authorization device that is used for theft prevention, particularly an engine immobilizer. The keys taught are then authorized to start up the vehicle. To this end, the keys each have an integrated transponder that can set up a radio link to a transmission unit in the authorization device for the interchange of data telegrams.
The currently most widely used method for teaching a plurality of keys to an authorization device in a vehicle provides for the transmission unit of the authorization device to transmit a teaching signal and for all the keys that are in the reception range to respond thereto, with only that key with the strongest response signal being recognized by the authorization device. As a result, the keys need to be brought into the proximity of the transmission unit in succession, the result of which is many manual interventions and a long process time.
DE 10 2008 052 239 A1 discloses a method for automatically teaching a plurality of keys to an engine immobilizer in a vehicle, wherein each key is assigned a different address in advance and during the teaching the respective key is selectively addressed by the engine immobilizer using the assigned address. This method therefore requires an upstream step in which the keys intended for the vehicle need to be assigned individual addresses. This extends the period of time for teaching the keys and there is a need for manual interventions in the procedure.
The generic DE 101 12 573 A1 describes a method for initializing a theft prevention system for a motor vehicle, wherein the theft prevention system first of all transmits a test signal. Each encoder that receives the test signal produces a transmission time that is characteristic of the respective encoder using a random principle, and a response signal is then transmitted within this transmission time. If it is not possible to distinguish between all the encoders, for example because two or more encoders have produced an identical transmission time, then the method starts afresh for the indistinguishable encoders until all the encoders have been recognized. The use of a random principle means that there is therefore always the possibility for a plurality of method cycles to have to be performed until all the encoders have been recognized.